From 9883975050deffc147a3903d07ff995ecdc8a100 Mon Sep 17 00:00:00 2001 From: Alberto Garcia Date: Fri, 3 Nov 2017 16:18:51 +0200 Subject: qcow2: Prevent allocating L2 tables at offset 0 If the refcount data is corrupted then we can end up trying to allocate a new L2 table at offset 0 in the image, triggering an assertion in the qcow2 cache that would crash QEMU: qcow2_cache_entry_mark_dirty: Assertion `c->entries[i].offset != 0' failed This patch adds an explicit check for this scenario and a new test case. Signed-off-by: Alberto Garcia Reviewed-by: Max Reitz Message-id: 92dac37191ae7844a2da22c122204eb493cc3133.1509718618.git.berto@igalia.com Signed-off-by: Max Reitz --- block/qcow2-cluster.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'block') diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index fb10e26068..2e072ed155 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -278,6 +278,14 @@ static int l2_allocate(BlockDriverState *bs, int l1_index, uint64_t **table) goto fail; } + /* If we're allocating the table at offset 0 then something is wrong */ + if (l2_offset == 0) { + qcow2_signal_corruption(bs, true, -1, -1, "Preventing invalid " + "allocation of L2 table at offset 0"); + ret = -EIO; + goto fail; + } + ret = qcow2_cache_flush(bs, s->refcount_block_cache); if (ret < 0) { goto fail; -- cgit v1.2.3